To delete the user key. For the set behavior: Set it to delRsaKey(2) to delete the RSA user key, to delDsaKey(3) to delete the DSA user key, or to delBothKeys(4) to delete both RSA and DSA user key. For the get behavior: You will get delRsaKey(2), delDsaKey(3) or delBothKeys(4) when the delete operation is in progress. Otherwise, you will get noDel(1).